New York ? For all their complaining as they pay $3 a gallon or more to fill up their cars, few American drivers have yet to reach the point of cutting back.

That’s the message from government statistics showing that demand for gasoline is only just starting to level off even as refinery outages and tight supplies have sent pump prices soaring by 43 percent since the end of January.

And brace yourself: Experts say with gas already closing in on $4 a gallon in Chicago and San Francisco ahead of the peak summer driving season, higher prices could be in the cards.

Most Americans are locked into their driving habits, and can do little to alter their fuel-buying patterns when prices rise. For example, the number of workers with commutes lasting longer than 60 minutes grew by almost 50 percent between 1990 and 2000, according to Census Department data.

But that usually means they have to cut back elsewhere, as Wal-Mart Stores Inc. is finding to its distress. The world’s largest retailer said Tuesday that earnings in the current quarter will fall short of Wall Street expectations, in part because of higher gas prices.

Experts disagree on how high prices have to rise before consumers are shocked into driving less – at least temporarily. While many see a psychological barrier at $3.50, some say the tipping point is more likely $4 a gallon.

There was a definite consumer reaction in September 2005 after Hurricane Katrina outages pushed prices above $3 for the first time. Demand dropped as much as 6.5 percent. Since then, however, consumers seem to have adapted, with demand rising throughout a brief period of prices above $3 a gallon last summer.

“People complain about higher oil prices … but they still drive their cars, they still buy their SUVs, they don’t want to carpool,” said Fadel Gheit, an energy analyst at Oppenheimer & Co.